1. Field of the Invention
The present invention relates to a medical adhesive tape or sheet and a first-aid adhesive tape. More specifically, the present invention relates to a medical adhesive tape or sheet and a first-aid adhesive tape used in medical uses in fields of adhering products, particularly rolled bandage, surgical tape, plaster, poultice, dressing member, wound protector and percutaneous absorption preparation. The above-stated medical adhesive tape or sheet and a first-aid adhesive tape are also suitable for use in aged persons, infants and sickly persons, who are susceptive to irritation to their skin.
2. Description of the Related Art
Conventionally, many films comprising a plasticized polyvinyl chloride as a main component prepared by a calender method or a sol cast method have been used as various medical adhesive tapes or sheets such as a first-aid adhesive tape or a surgical tape.
A film for a supporting substrate comprising this plasticized polyvinyl chloride as a main component has the characteristic that it shows high stress at a tensile initial stage, but stress relaxation rapidly occurs with the passage of time. This stress relaxation is due to plasticity of the polyvinyl chloride film. In the case where an adhesive tape or sheet that includes a film for a supporting substrate having such a characteristic is adhered to a skin, tensile stress is gradually relaxed after the adhering, resulting in a reduction of load to the skin. Thus, with use of the supporting substrate film comprising the plasticized polyvinyl chloride as a main component, adhering workability is secured by an appropriate stress when adhering, and also a tense feeling is eliminated by the subsequent stress relaxation, so that physical irritation to the skin is alleviated. This imparts the tape or sheet with both good operability and low skin-irritating property.
However, if the plasticized polyvinyl chloride is used, a large amount of plasticizer is contained and such a plasticizer migrates from the film to the adhesive layer. As a result, there are disadvantages of a lowered adhesive force or a lowered cohesive force, the adhesive modifies, or the adhesive fluidizes to thereby stain a circumference portion of the adhering site.
Further, since the film contains chlorine atoms, there is a need for a countermeasure on its post-treatment from the standpoint of a recent environmental problem.
For this reason, there has been active development of flexible and stretchable thermoplastic resins as a substitute material of vinyl chloride, not limited on medical uses, and many thermoplastic resins have been commercialized in olefin resins, ethylene-vinyl acetate copolymer (EVA) resins or elastomer resins.
Specific examples of the commercialized products include ethylene-methacrylate (EMA) resins, amorphous poly-xcex1-olefin resins, ethylene-vinyl acetate copolymer (EVA) resins, olefin resin/EMA blends, polyurethane resins, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) resins and ethylene-methyl methacrylate copolymer (EMMA) resins. Of those, from the standpoint of providing elastic, non-chlorine-containing material, thermoplastic elastomer (TPE) resins have been recently actively investigated as an effective material that achieves the above objects.
As the thermoplastic elastomer resins, for example, styrene-based thermoplastic elastomers (SBC) such as styrene-butadiene-styrene block copolymer (SBS) were first developed, and subsequently engineering plastic-based TPE such as thermoplastic vinyl chloride-based elastomers (TPVC), thermoplastic olefin-based elastomers (TPO) or ester olefin-based elastomers (TREE) have been developed. In particular, the thermoplastic olefin-based elastomers (TPO) are in a position most close to polyvinyl chloride in weather resistance and cost.
Further, in recent years, an improved TPO to be scratchless has been developed, and this improved TPO includes a polypropylene-based polymer alloy obtained by blending a novel, high blend-type hydrogenated styrene-butadiene copolymer (hydrogenated SBR).
Those various resins may be used as a substitute of the vinyl chloride resins; however, a portion of the above thermoplastic elastomers is merely utilized for medical uses only in areas such as an infusion bag, a waste bag for artificial dialysis or infusion tube.
On the other hand, it is attempted to apply flexible olefins such as the above-described amorphous poly-xcex1-olefin resins as a substitute film of the vinyl chloride resins to a medical film for a supporting substrate. However, it cannot be said that those are the most appropriate, in view of the following points.
That is, there has been the problem of very poor operability for adhesion in actual spots of medical treatment even if the flexible olefins are low in stress no matter how strong tension or elongation exerted thereon is. Alternatively, when the rubber elasticity is too high, the stress upon deformation becomes too high to the contrary, resulting in that a tension is successively exerted on the skin while the tape or sheet is being adhered so that there occurs an increased physical irritation to the skin.
Thus, opposite properties of good operability for adhesion and low irritating property to the skin cannot sufficiently be satisfied if the conventional vinyl chloride-free resins are only directly used as a film for a supporting substrate of a medical adhesive tape or sheet.
From this standpoint, there have been several proposals for utilization of thermoplastic elastomers as a film for supporting substrate of a medical adhesive tape having the same stress relaxation property as in the vinyl chloride resins. Thermoplastic resins having such a high stress relaxation property include olefin-based resins blended with large amounts of rubber components and amorphous olefin-based resins.
In the conventional olefin-based thermoplastic elastomers, a blend-type thermoplastic elastomer in which a polypropylene (PP) is a hard segment and an ethylene-propylene rubber (EPR) is a soft segment has been a leading elastomer. However, in the case of PP/EPR, which is a general simple blend, it has been difficult to blend therewith a large amount of rubber in a uniformly dispersed state so that it has been difficult to sufficiently exhibit merits of alloy formation (i.e., achieving both heat resistance and flexibility, improvement in stress relaxation.
On the other hand, to solve the problems, the system in which polymer alloy is produced in the step of polymerization has been developed.
Examples of the olefin-based thermoplastic elastomers (reactor TPO) that can directly be produced at the polymerization step include FPO (Flexible Poly Olefins) of Rexene Co., Catalloy resin of Montell Polyolefins Co. and PER resin of Tokuyama Soda Co.
Catalloy resin is a resin obtained by alloying an ethylene-propylene rubber in an olefin resin at the polymerization step, and has excellent characteristics in heat resistance, tear strength and piercing strength as compared with other flexible resins (such as PVC or PE-based resins). The resin is obtained by a polymerization process technique that enables a polyolefin to be alloyed in a polymerization reactor. The polymerization process technique comprises multi-stage gas phase polymerization reactors, in each of which polymerization is independently conducted, and a polymer obtained in the respective reactor is taken out in an alloyed state as a final product. In this process, a synthetic rubber (ethylene-propylene rubber) is blended at the polymerization step, and a polymer resin having considerably high rubber content is obtained as compared with blending with an extruder or the like. As a result, it is possible to closely harmonize high elasticity of polyolefin and flexibility of rubber, so that the alloyed resin can have high initial elastic force and rapid stress relaxation property.
Further, examples of the amorphous olefin-based resin include APAO (Amorphous Poly Alpha Olefin) resin and CAP resin, products of Ube Industry Co. Those resins are excellent in flexibility and heat resistance and are also relatively excellent in stress relaxation property, as compared with the conventional olefin-based resins.
APAO resins are seldom used alone but they are blended with polypropylene or commercialized as a multilayer film having laminated thereon an outer layer of other olefin-based resin. In such a case, they have relatively high stress relaxation property.
However, even if the above Catalloy resin or amorphous poly-xcex1-olefin-based resin is used, an initial stress is virtually too high, so that there may the case where a tense feeling just after adhering is strong. Further, relaxation tendency becomes extremely dull after relaxation has occurred to a certain degree or more, so that there is the tendency that a limit is observed in achieving flexibility by stress relaxation. Furthermore, the speed of stress relaxation leading to flexibility is clearly lower than that of the film composed of flexible polyvinyl chloride resin. In particular, even a small load to a skin, if it remains sustained, may cause some users an apparent irritation to the skin.
Further, the above resins not only give a poor feeling but also poor appearance when they are used in a medical adhesive tape or a first-aid adhesive tape.
The present invention has been made in view of the above-described disadvantages.
Accordingly, it is an object of the present invention to provide a medical adhesive tape or sheet, and a first-aid adhesive tape, suitable for adhering to bending portions or the like by using a supporting substrate having appropriate flexibility and stress relaxation property as well as good feeling as a substitute of a film for a supporting substrate made of a polyvinyl chloride resin.
As a result of intensive investigations, the present inventors have found that the above object can be achieved by using a composition containing a thermoplastic resin and a silicic acid compound in certain proportions for a supporting substrate. The present invention has been completed based on this finding.
More specifically, the present invention provides the followings:
1) A medical adhesive tape or sheet comprising a supporting substrate and an adhesive layer directly or indirectly laminating thereon, wherein the supporting substrate comprises a composition which comprises 100 parts by weight of a thermoplastic resin and 10 to 200 parts by weight of a silicic acid compound.
2) The medical adhesive tape or sheet as described in 1) above, wherein the silicic acid compound is at least one selected from the group consisting of zeolite, talc and silica.
3) The medical adhesive tape or sheet as described in 1) above, wherein the thermoplastic resin is at least one member selected from the group consisting of a polypropylene resin, a blend of a polypropylene resin and an elastomer, and a copolymer of a polypropylene resin and an elastomer.
4) The medical adhesive tape or sheet as described in 3) above, wherein the polypropylene resin, or the copolymer of a polypropylene resin and an elastomer is amorphous or low crystalline.
5) The medical adhesive tape or sheet as described in 4) above, wherein the amorphous or low crystalline polyolefin resin is present in an amount of 30 to 100% by weight based on the total weight of film-forming materials for a supporting substrate.
6) The medical adhesive tape or sheet as described in 1) above, wherein the supporting substrate further comprises a resin modifier.
7) The medical adhesive tape or sheet as described in 6) above, wherein the resin modifier is present in an amount of 0.1 to 40% by weight based on the total weight of the film-forming resin composition.
8) The medical adhesive tape or sheet as described in 6) above, wherein the resin modifier is at least one selected from the group consisting of a hydrogenated product of styrene-butadiene copolymer or its maleic acid-modified product, polystyrene-polyethylene.butylene-crystalline polyolefin, crystalline polyolefin-polyethylene.butylene-crystalline polyolefin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid ester-maleic anhydride copolymer, ethylene-methacrylic acid glycidyl ester copolymer, maleic anhydride graft polypropylene, maleic anhydride graft ethylene-polypropylene copolymer, acrylic acid graft polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate/ethylene-propylene-diene/polyolefin graft copolymer, metal salts of ethylene-methacrylic acid copolymer and chlorinated paraffin.
9) The medical adhesive tape or sheet as described in 1) above, wherein the supporting substrate has a stress relaxation ratio of 60% or less.
10) A first-aid adhesive tape comprising the medical adhesive tape or sheet as described in 1) above, and an absorbent pad provided at a central region on a surface of the adhesive layer thereof.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of preferred embodiments.